1. FIELD OF THE INVENTION
This invention relates to fuel elements for nuclear reactor cores and, more specifically, to apparatus for restraing fuel element motion during reactor operation, and the like.
2. BACKGROUND
Normally, the fuel assemblies are densely spaced and the coolant medium, which can be a liquid or gas, flows vertically upward in longitudinal direction. The flow can stress the fuel assemblies or the fuel rods, so that vibrations are induced. Due to variation in the coefficients of heat expansion of the various materials used in nuclear constructions, it is not possible to rigidly attach the fuel assemblies to the lower and the upper grid plates which are integral parts of the core support structure. Therefore, it was already suggested (OS 21 40 170) to provide elastic (spring) elements to press the fuel assemblies against the two grid plates. Such arrangement has the disadvantage that the elastic element with its compression spring is located in the flow path which causes an undesirable pressure drop, which on large reactors may attain considerable values. The inlet pressure of the coolant must be increased which is equivalent to a reduction of reactor efficiency.
The purpose of the invention is to support the fuel assemblies simply, safely, free of vibration and without an increase of the flow resistance of the coolant.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages ans specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention .